A single-wafer type liquid processing apparatus employed in a semiconductor manufacturing process is configured to discharge a processing liquid onto a surface of a substrate held on a spin chuck from a nozzle, for example. Examples of liquid processing include a process of coating a resist solution on a substrate to form a resist pattern, a process of supplying a developing solution onto a substrate after exposure, a process of cleaning a substrate by supplying a rinse liquid onto a substrate, and so forth. This processing liquid is supplied into the nozzle through a pipeline which is equipped with such devices as a valve, a filter and a pump.
A flow path including a device or a pipeline is made of an insulating material such as a fluorine resin for the purposes of cleanness or chemical resistance. As known in the art, if a processing liquid is flown into the flow path, static electricity is generated by friction between the flow path and the processing liquid. Depending on the kind of the processing liquid or the processing condition, a charge amount may be increased. As a result, there is a concern that a member forming the flow path is damaged caused by dielectric breakdown thereof or a processing efficiency is deteriorated.
Patent Document 1 describes a method of neutralizing electric charges by grounding the processing liquid via a carbon electrode which is configured to be in contact with the processing liquid. However, there is a concern that the carbon electrode having high purity may be broken or damaged. If an element other than carbon is contained, an impurity may be eluted in the processing liquid, causing contamination of the processing liquid. Further, in the disclosure of Patent Document 1, since the charge amount of the processing liquid cannot be detected, it is difficult to take a response to the charging.
Patent Document 1: Japanese Patent Laid-open Publication No. 2006-269677 (paragraphs [0036] and [0063], FIG. 2, etc.)